Electric resistance furnace adapted for heating by nitrogenization



A. FRY

March 6, 1928.

ELECTRIC RESISTANCE FURNACE ADAPTED FOR HEATING BY NITROGBNIZATION FiledAug. 2, 1926 2 Sheets-Sheet l March s, 1928. A. m 1,6 1, 94.

ELECTRIC RESISTANCE FURNACE ADAPTED FOR HEATING BY' NITROGENIZATIONFiled Aug. 2, 1926 2. Sheets-$heet 2 Fig.3.

@WM 1 Wij%% Patented Mar. 6, 1928.

UNITED STATES HEISSUED "661,694

PATENT OFF-ICE.

ADOLI FRY, ISBEN-ON-TEE-BUHR,

GERMANY, ASSIGNOB TO FRIED. KBUPP AKTIENGESELLSCHAFT, 0FESSEN-ON-THE-BUHB, GERMANY.

Application filed August 2, 1926, Serial No.

The purpose of the invention is to provide an electrical resistancefurnace for hardening by nitrogenization which is char-,

In order to allow 9f my invention to be more readil understood anexample of embodiment -o the same Wlll now be described in detail withreference to the drawings which accompany and form part of thisspecification, this embodiment s owin sistance furnace o erated b ,means0 three base current an designs to be used for ,15 ardening steelarticles by nitrogenization.

In these drawings Fi 1 is a longitudinal section through the urnace,

Fig. 2 is a section on line 2-2 of Fig. 1, Fi 3 is the correspondingwirediagram. Re erring now first to Figs. 1 and 2, A denotes thebrickwork of the furnace into the foundation .of which a plurality ofpillar blocks B of refractory material are built in. These blocks B,form supports .for a box D of rectangular cross section which is open atits ends and rests on said blocks B by means of cross carriers G. Thebox D is made of a heatand corrosion-proof alloy, forinstance achromium'nickel steel alloy and is provided which is su divided so as toform three phase-windin and consists of .chromiumnickel-iron wire. Theends'of these windings E, E, E, Fig. 3, are led out of the furnacethrough its. wall in a suitable manner (not shown) and so connected, bymeans of a four-pole throw-over switch F, Fig. 3, to a three-phase mainG, thatin the switch osition denoted .by I, star connection and inposition II series connection of said three phase-windings E, 'E, E isestablished.

By means of suitable screw bolts 1& the box D is suspended from crosscarriers H which rest on the side wallsof the brickwork. The furnace iscovered on the top by an iron cover plate J loosely resting on thebrickwork A and after the removal of which the box D together with thecarriers H may be removed as a whole. The hollowspaces existing betweenbox D and brickwork A and cover J are. filled with kieselguhr, as shownin Fig. 2. w

are-- on its outer surface with insulators -'(not shown) car 'ng theheating resistance E 128,850, and in Germany September 4, 1925.

The box D is fitted with a track consisting M of three U-iron rails K,see Fig. 2, riveted to the floor of the box, and of guide ribs k.Similar tracks K and K projecting into box D through the front openingsof the furnace form prolongations of track K, k at both ends of the boxand are arranged outside the furnace in the manner shown in Flg. 1. Asystem of loose double rollers M 18 adapted to run on the rails K, K, K,said rollers being interconnected by axles m and lateral frame-plates'm. so as to form a moving platform. The length of the whole roller sstem M m 'm is about double and a half te length of the furnace.

A receptacle P, designed to receive the articles to be nitrogenized, isresting, within the heating chamber formed by the box D,

through the intermediary of a bottom plate N, on the loose rollers M, aneye serving to attach a wire rope or the like being rovided on it. Thereceptacle P is closed in a gas-tight manner by a cover p and is made ofa chromium-nickel-steel alloy having a particularly high resistance toheat and chemical-influences. The supply of the gas delivering nitrogento the receptacle P takes place through a pipe passing through one ofits front walls an reaching nearly up to the other front wall thereof. Aipe p passin through the same front wal serves to lea oif the gas. Asecond, similar receptacle R rests outside the furnace on that portionof the moving platform M m 'm which rests on the track portion denotedby K The heating chamber of the furnace is shut off from the outer spaceby loose walls Q which have to be removed before the rece tacle P isentered.

he operation of the described resistance furnace takes place as follows.

After the furnace, still empty but closed by the loose walls Q, has beenheated up by connecting the resistances E E E to the three-phase main Gwith the throw over switch F in position I (star connection), the switchF is turned over into position II, in which the phase windings take onlyso much current as it is suflicient to maintain the temperature attainedby the heating-up operation. The receptacle P which has been filled inthe meantime with the articles to be hardened and closed in gas-tightman- The nitrogenous her, is then entered, after removal of the loosewalls Q, into the heating chamber of the furnace. When this takes place,the moving glatform displaces itself with half the spec of thereceptacle P. After the ipes p and p have been connected to a gottlecontaining the nitrogenous gas, the furnace is closed again by the loosewalls Q.

as is thereupon supplied to the receptacle Plieated by means of theresistances E E E. Dunn this operation nitrogen enetrates the artcles-to be hardened and; ardens them. During the period ofnitrogenization the second rece tacle, R, is put on the track portion Kand lled with articles, to be hardened. As soon as a suflieient quantityof nitrogen has been supplied the articles containedin receptacle andreceptacle R has been filled, the loose walls Q'are' removed. Thereceptacle P is thereupon shifted in the direction of arrow m,

Fig. 1.- This motion is taken part inrby the moving platform'with halfthe speed, and by the receptacle R with the speed of the recep; tacle P.When the receptacle R has reached the former position of rece tacle P,the latter which now is outside the urnace, is brought I to a standstilland the loose walls Q are enized and rece tacle P is emptied and re-'brou ht into positionagain. This done, the artic es containedinreceptacle R are nitrogfilled with artic es to be hardened, so that itenters the furnace at the same time when res ceptacleR leaves it. Fromthis time the described operations maybe repeated'as, often asdesired.Finally'the furnaceis thrown out of operation by interrupting thecurrent su 1y. p l' he fact thatthe electric heating body D is capableof receiving a shiftable' receptacle enables a great number of articlesto be treated at the. same time andin a very easy manner! In comparisonwithv receptacles running on wheels the arrangementof the receptacle Pand R on the described roller system offers the very important advantageof the pulling in and out of the filled receptacles taking place in avery any manner.

By making the heating box and the receptacle of a chromium-nickel-steelalloy which has a high resistance to heat and chemical influences (andmight be re laced by any other suitable metal or alloy not only the lifeof the heating box and of the is pre-heated up to the treatingtemperature comes into contact with the articles to be hardened.

The closure of the receptacles by means of a removable cover offers theadvantage, in

comparison with the front wall closures hitherto used with resistancefurnaces, that the articles to be treated may be more easily set in andout and may be carefully embedded.

' Withoutdeviating from the spirit of the invention, the furnace mightbe closed by sliding doors instead of by loose walls.

Furthermore, the described furnace is adapted to be used, instead of thedescribed nitrogenization, for the cementation of steel oth'er'heattreatment, for instance I or for any for heating articles in aninertgas.-

I claim: 1 f

In an electric resistance furnace adapted for hardening metals bynitrogenization, a roller system, a nitrogenizing receptacle mountedthereon, and a removable electrically' heated casing surrounding saidnitrogenizing receptacle and the portion of the roller system which lieswithin the furnace.

The U foregoing specification h signed at Cologne, Germany, this 10 dayof July, 1926.

ADOLF FRY.

